There is a rectangle of size .
This rectangle will be filled with with square tiles without any remaining spaces. You can purchase square tiles as follows:
- By paying a cost of , you receive square tile of size .
Find the minimum cost required to fill the entire rectangle with square tiles without any remaining spaces.
Input
The input is given in the following format.
Output
Print the minimum cost required.
Constraints
- .
- .
Subtasks
Samples
입력
6 4
출력
8
If you use square tiles with a side length of , the cost is . However, this is not optimal.
Instead, if you fill it with one square tile with a side length of and two square tiles with a side length of , the cost is . It can be shown that is the minimum cost.